Micro-switch is a miniaturized switch with a transmission shaft formed in a selected shape on an outer side to receive an external force to perform switching operation. It generally includes features such as a small contact distance and an instant moving mechanism to provide mechanical ON/OFF through a set moving distance and action force, thus is often used to detect positioning status of machine movement.
A conventional micro-switch such as R.O.C. patent No. 592380 mainly includes an upper lid and a base. The micro-switch also includes a pushbutton, a common pin, an open-circuit pin and a conductive reed fastened to the common pin. One end of the conductive reed is depressible by the pushbutton so that another end of the conductive reed is moved downwards at the same time to connect the common pin and open-circuit pin to generate a switch signal. While it can provide circuit switch function, it relies merely on the conductive reed to bear the downward pressure and provide an elastic force. After used for a prolonged period, the reed tends to fatigue because of frequent bending up and down or even fracture, and could result in dysfunction of the micro-switch.
To remedy the aforesaid shortcoming, China utility patent CN202110987 discloses a micro-switch capable of withstanding a greater number of pressing, referring to FIG. 1. It comprises a housing 1, a plurality of conductive terminals 2 located on the housing 1, an elastic element 3, a conductive reed 4 and a pushbutton 5. The conductive reed 4 has a press-receiving portion 41 to receive pressing of the pushbutton 5, a contact portion 42 located between the conductive terminals 2, and at least one connection rib 43 to bridge the press-receiving portion 41 and contact portion 42. The elastic element 3 bridges the conductive reed 4 and conductive terminals 2. The conductive reed 4 is supported by the elastic element 3 in normal conditions. The elastic element 3 provides a bracing force for the conductive reed 4 to prevent it from incurring fatigue and fracturing caused by repetitive up and down swaying. Therefore the conductive reed 4 has a longer lifespan and can withstand a greater number of depressing.
Although the aforesaid technique resolves the problem of easy fatigue and fracturing of the conductive reed, and can withstand a greater number of pressing, it still has the following drawbacks remained to be overcome: when the pushbutton 5 is pushed downwards to press the press-receiving portion 41 the contact portion 42 also is moved downwards. As the conductive reed 4 is formed at a considerable length and thickness, a substantial push force has to be applied to the pushbutton 5 to sway the contact portion 42 to move to and fro at a sufficient distance to switch between different conductive states. To reduce the push force, one of the approaches is to reduce the thickness of the conductive reed 4 that is more difficult in fabrication and also results in decreasing of the lifespan of the conductive reed 4. Moreover, a great current often occurs during connection of the contact portion 42 and conductive reed 4 that generates a greater amount of heat on the contact surface between the contact portion 42 and conductive reed 4 and could cause melting of a portion of the contact portion 42 to stick to the conductive reed 4, then a greater force has to be applied to separate the contact portion 42 and conductive reed 4 to make the micro-switch function normally. Hence to overcome the sticking phenomenon is the prerequisite condition to reduce the press force needed for switching. This is still an issue remained to be resolved.
In addition to the considerations of increasing the lifespan of the micro-switch and reducing the press force for switching, a wide variety of specifications also are required in various industries to fabricate different types of precision machineries. Those varying specifications of micro-switches have specific moving distances and action forces. For instance, while reducing the thickness of the elastic reed can make the action force smaller, changing the moving distance involves assembly of a greater number of internal elements. Merely changing one element cannot meet the requirements of various specifications. Hence the producers have to make a greater number of molds that also makes the production higher. Thus how to change the moving distance of the micro-switch easier through a same production mold is another problem pending to be overcome.